A field defence or rampart which was made of felled trees with the sharpened boughs facing outwards, towards the direction of attack. (O.Fr. enbatre, to thrust in).

Absolute Pressure

Gage pressure plus atmospheric pressure.

Absolute Pressure Transducer

A transducer which measures pressure in relation to zero pressure (a vacuum on one side of the diaphragm).

Absolute Zero

Temperature at which thermal energy is at a minimum. Defined as 0 Kelvin, calculated to be -273.15 C or -459.67 F.

Abutment

the outermost end supports on a bridge, which carry the load from the deck

Ac

Alternating current; an electric current that reverses its direction at regularly recurring intervals.

Acceleration

A change in the velocity of a body or particle with respect to time. The parameter that an accelerometer measures (dv/dt). Units expressed in "g".

Accelerometer

A device which converts the effects of mechanical motion into an electrical signal that is proportional to the acceleration value of the motion. A sensor. A transducer.

Accuracy

The closeness of an indication or reading of a measurement device to the actual value of the quantity being measured. Usually expressed as percent of full scale output or reading.

Acoustics

The degree of sound. The nature, cause, and phenomena of the vibrations of elastic bodies; which vibrations create compressional waves or wave fronts which are transmitted through various media, such as air, water, wood, steel, etc.

Activity (ai)

A thermodynamic term for the apparent or active concentration of a free ion in solution. It is related to concentration by the activity coefficient.

Activity Coefficient (fi)

A ratio of the activity of species i(ai) to its molality (C). It is a correction factor which makes the thermodynamic calculations correct. This factor is dependent on ionic strength, temperature, and other parameters.

Adapter

A mechanism or device for attaching non-mating parts.

ADC

Analog-to-Digital Converter - an electronic device which converts analog signals to an equivalent digital form, in either a binary code or a binary-coded-decimal code. When used for dynamic waveforms, the sampling rate must be high to prevent aliasing errors from occurring.

Address

The label or number identifying the memory location where a unit of information is stored.

Adultrine Castle

The unlicensed castles (probably of the motte and bailey type) were constructed without royal permission by the Barons supporting Matilda in England during the reign of Stephen (1136-1152), and were demolished by Henry II after the treaty of 1153.

Advanced Work

An outer defence of a fortification situated beyond the glacis but placed close enough to receive covering fire from the main works. See outwork, ravelin.

Agger

The rampart formed by heaping the excavated soil up on the inner side of ditch surrounding a Roman fortification.

Aile

A wing or flank of a fortification.

Alatorium

The Latin term for the wall walk behind the battlements of a fortification, which enables the defenders to protect their position from the tops of the walls. Also known as an allure or parapet walk. See allure.

(1) A bridge connecting separate towers of Andalusian fortifications.(Spanish) (2) A tower connected to the curtain wall by a bridge.

Alcasar, Alcazar, Alkazar

When an alcazabar was rebuilt and enlarged in stone it became an alcazar, which was used as fortified palace of the regional military governor.

Alcazabar

A stronghold built by the Saracens in Spain. The irregular walls of the enceinte followed the contours of a defensible hill, and the curtain was reinforced by square or polygonal towers. They were constructed chiefly of tapia, a mixture of cement and pebbles poured between boards, thus the material was not suitable for round towers, producing square and polygonal shapes.

Aliasing

If the sample rate of a function (fs) is less than two times the highest frequency value of the function, the frequency is ambiguously presented. The frequencies above (fs/2) will be folded back into the lower frequencies producing erroneous data.

Alloy 11

A compensating alloy used in conjunction with pure copper as the negative leg to form extension wire for platinum-platinum rhodium thermocouples Types R and S.

Alloy 200/226

The combination of compensating alloys used with tungsten vs. tungsten 26% rhenium thermocouples as extension cable for applications under 200 C.

Alloy 203/225

The combination of compensating alloys used with tungsten 3% rhenium vs. tungsten 150 rhenium thermocouples as extension cable for applications under 200 C.

Alloy 405/426

The combination of compensating alloys used with tungsten 5% rhenium vs. tungsten 26% rhenium thermocouples as extension cable for applications under 870 C.

Allure, Alur, Alure

A passage or gallery behind a parapet at the top of a wall of a fortification. Also known as a bailey walk, parapet walk, wall walk and wall walkway. See alatorium. (O.E. alours).

Almenara (Atalaya)

A small fort used as a watchtower on the Iberian peninsula. (Arabic)

Alphanumeric

A character set that contains both letters and digits.

Alternating Staircase

A staircase which was used for communication between different floors of a tower or keep. The staircase reversed its turn from right-to-left to left-to-right from floor to floor. This design was used to break the flow of the enemy's advance once they had gained entry to the keep.

ALU

Arithmetic Logic Unit. The part of a CPU where binary data is acted upon with mathematical operations.

Alumel

An aluminum nickel alloy used in the negative leg of a Type K thermocouple (Trade name of Hoskins Manufacturing Company).

Aluminum

a lightweight chemical element (Al); the most abundant metallic element in the Earth's crust

Ambient Compensation

The design of an instrument such that changes in ambient temperature do not affect the readings of the instrument.

Ambient Conditions

The conditions around the transducer (pressure, temperature, etc.).

Ambient Pressure

Pressure of the air surrounding a transducer.

Ambient Temperature

The average or mean temperature of the surrounding air which comes in contact with the equipment and instruments under test.

A unit used to define the rate of flow of electricity (current) in a circuit; units are one coulomb (6.28 x 1018 electronics) per second.

Amplifier

A device which draws power from a source other than the input signal and which produces as an output an enlarged reproduction of the essential features of its input.

Amplitude

A measurement of the distance from the highest to the lowest excursion of motion, as in the case of mechanical body in oscillation or the peak-to-peak swing of an electrical waveform.

Amplitude Span

The Y-axis range of a graphic display of data in either the time or frequency domain. Usually a log display (dB) but can also be linear.

Analog Output

A voltage or current signal that is a continuous function of the measured parameter.

Analog-to-Digital Converter (A/D Or ADC)

A device or circuit that outputs a binary number corresponding to an analog signal level at the input.

Anbar

A fortified barracks of the Sassanian empire. (Sassanian)

Anchorage

a secure fixing, usually made of reinforced concrete to which the cables are fastened

Anemometer

An instrument for measuring and/or indicating the velocity of air flow.

Angle

Angle of the centre of a polygon;

Angle Of The Flank

The angle of the flank is the angle between the curtain and the adjacent flank, also known as the; curtain flank and the flanking angle.

Angle Of The Polygon

The angle of the polygon is formed by the junction of the two adjacent sides of a polygon.

Angstrom

Ten to the minus tenth meters (10-10) or one millimicron, a unit used to define the wave length of light.

Angular Frequency

The motion of a body or a point moving circularly, referred to as the circular frequency O which is the frequency in cycles per second (cps) multiplied by the term (2) and expressed in radians per second (2pf).

Anion

A negatively charged ion (Cl-, NO3-, S2- etc.)

ANSI

American National Standards Institute.

Antemural

A breastwork or a strong wall provided with towers which project from an outwork, also called a barbican.

Antesture

A small trench or work formed of palisades.

Anti-reset Windup

This is a feature in a three-mode PID controller which prevents the integral (auto reset) circuit from functioning when the temperature is outside the proportional band.

Application Program

A computer program that accomplishes specific tasks, such as word processing.

The trenches which were dug towards a fortress running from the parallel trenches of a besieging force, the trenches were dug in a zigzag pattern so that the occupants were not exposed to enfilade fire from the guns of those besieged in the fortress. (Fr.) See sap, zig zag.

Apron

(1) The portion of the superior slope of a parapet. (2) The interior slope of a pit designed to protect the rampart against blast. (3) The sloping plinth or batter of a fortifications walls and/or towers. See batter, plinth, talus.

Apsidal Keep

A Welsh keep built on a rectangular plan but with one of its sides rounded.

Aqueduct

a bridge or channel for conveying water, usually over long distances

Arc Of Fire

The scope or number of degrees of the field of fire a projectile weapon has when firing through an aperture in the wall of fortification, such as; an arrow slit, gun port, crenel or an embrasure.

Arch Bridge

a curved structure that converts the downward force of its own weight, and of any weight pressing down on top of it, into an outward force along its sides and base

Arch Dam

a dam with an arched shape that resists the force of water pressure; requires less material than a gravity dam for the same distance

Arch Machicolation

See machicolation, pointed arch machicolations.

Architect

A person who designs all kinds of structures; must also have the ability to conceptualize and communicate ideas effectively -- both in words and on paper -- to clients, engineers, government officials, and construction crews

Arrow

An outwork consisting of two parapets fronted by a ditch, situated at the salient angle of the glacis, and was connected to the covert-way by a caponier.

Arrow Headed Bastion

A bastion which was used in fortifications to provide flanking as well as covering fire while presenting the enemy with the smallest target possible by the virtue of its shape. Because of its characteristic arrow head shape it could be completely covered by two carefully placed guns in the neighbouring works, in return, a pair of guns in the flank of the bastion could efficiently sweep the straight wall on either side of at least 180 degrees to the front. A fortification employing such bastion in the before mentioned manner is said to have a 'bastioned trace'. See bastion, bastioned trace.

Arrow Loop

A narrow opening in the wall of a tower, curtain wall or merlon, which was used by archers to shoot through at the enemy without, with a limited amount of exposure to enemy fire. The arrow loops were carefully spaced in walls to avoid the creation of weak areas which would suspect to damage by siege weapons. The arrow loop was of generally two types

Arrow Slit

A narrow rectangular opening in the wall of a castle which was used by archers to fire through at the enemy beyond the walls. The earliest form of arrow slit consisted of a plain slit formed by leaving a gap between two adjacent stones of a wall. See arrow loop, loop.

A fortress designed specially to be defended by artillery, for example the artillery forts of Henry VII of England.

Artillery Outwork

See hornwork, ravelin.

Artillery Platform, Artillery Terrace

See gun platform.

Artillery Tower

A tower provided with cannon, especially reinforced to take the weight and recoil of the cannon, which were normally situated on the roof, giving them a height advantage over the artillery of the besiegers.

Ascensi Valli

The staircases or ramps used to reach the rampart walk of a Roman fort.

American Standard Code for Information Interchange. A seven or eight bit code used to represent alphanumeric characters. It is the standard code used for communications between data processing systems and associated equipment.

ASME

American Society of Mechanical Engineers.

Assembler

A program that translates assembly language instructions into machine language instructions.

Assembly Language

A machine oriented language in which mnemonics are used to represent each machine language instruction. Each CPU has its own specific assembly language.

ASTM

American Society for Testing and Materials.

Asymmetry Potential

The potential developed across the glass membrane with identical solutions on both sides. Also a term used when comparing glass electrode potential in pH 7 buffer.

Asynchronous

A communication method where data is sent when it is ready without being referenced to a timing clock, rather than waiting until the receiver signals that it is ready to receive.

1. A feature on a limit controller that automatically resets the controller when the controlled temperature returns to within the limit bandwidth set. 2. The integral function on a PID controller which adjusts the proportional bandwidth with respect to the set point to compensate for droop in the circuit, i.e., adjusts the controlled temperature to a set point after the system stabilizes.

AWG

American Wire Gage.

Axis Of Rotation (Spin Axis)

The axis of rotation (spin axis) is that straight line about which a body rotates.